I think the most important consideration when deciding upon any research topic is that it must be something that is of great interest to you personally. In this sense it is quite difficult for anyone else to give you many ideas, as only you will know what interests you. It is also important to choose a topic that you believe you can realistically research given your resources, time frames, ethical considerations etc. I think, in general, given the level of the research you are undertaking, it might be useful to look at previous research already undertaken and establish if you could usefully extend that, rather than attempting something too ambitious, by way of a completely new topic.